What Is a 401(k)? How It Works, Contribution Limits, and Employer Match

A 401(k) is an employer-sponsored retirement account that lets you contribute pre-tax dollars directly from your paycheck, reducing your taxable income today. In 2026, you can contribute up to $23,500 per year ($31,000 if you are 50 or older). The money grows tax-deferred until withdrawal in retirement, when it is taxed as ordinary income. Many employers also match a percentage of your contributions — the most powerful financial benefit most employees receive and the first lever to maximise.

How a 401(k) works: the mechanics

Each paycheck, you elect a percentage of your salary to contribute to your 401(k). That money is deducted before income tax is calculated. Example: if you earn $5,000/month and contribute 10% ($500), your taxable income for that paycheck is $4,500, not $5,000. At a 22% marginal bracket, you save $110 in federal income tax on that single paycheck. Over a year of 10% contributions on $60,000 salary, you defer $6,000 in income and save roughly $1,320 in federal tax (at 22% bracket).

Inside the account, you invest in a menu of options your employer provides — typically target-date funds, index funds, and actively managed mutual funds. The money grows tax-deferred: dividends, interest, and capital gains are not taxed each year. When you withdraw in retirement (age 59½ or later), withdrawals are taxed as ordinary income.

2026 contribution limits

The IRS also sets a combined limit (employee + employer contributions) of $70,000 in 2026. Most employees never approach this limit, but it is relevant for highly compensated employees whose employer makes large contributions.

The employer match: do not leave it on the table

An employer match is additional money your company deposits into your 401(k) based on your own contributions. A common structure: "100% match on the first 3%, 50% on the next 2%" means if you earn $80,000 and contribute 5% ($4,000), your employer adds $2,000 × 100% + $800 × 50% = $2,400. That is a guaranteed 60% return before any market performance.

Always contribute at minimum enough to capture the full employer match. This is the single most valuable financial action available to most employees. Skipping the match to prioritise other goals (even debt payoff) is usually a mistake — no debt has an interest rate of 50–100%.

Traditional vs Roth 401(k): which should you choose?

The core trade-off: Traditional saves you tax now at your current marginal rate. Roth saves you tax in retirement at whatever rate applies then. If you expect to be in a higher tax bracket in retirement than today, Roth wins. If you expect a lower bracket (typical for most workers), Traditional wins. If unsure, split between both — many plans allow you to designate some contributions to each.

A useful rule of thumb: if you are early in your career (lower income bracket now, higher later) or if tax rates generally might rise over your career, lean toward Roth. If you are in your peak earning years at a high bracket, Traditional reduces taxes more aggressively right now.

What to invest in inside your 401(k)

Most 401(k) plans offer three categories of investments:

• Target-date funds (e.g., "2055 Fund"): All-in-one fund that automatically adjusts its stock/bond mix as you approach the retirement year. The simplest option and appropriate for most participants — pick the fund whose year is closest to your expected retirement.
• Index funds: If your plan offers them (look for "index" in the name), these passively track a market index at low cost (0.03–0.20% expense ratio). A Total Stock Market Index fund + a Total Bond Index fund is a classic two-fund portfolio.
• Actively managed funds: Higher fees (often 0.5–1.5%), and research shows 85–90% underperform their benchmark index over 10 years. If your only options are active funds, choose the ones with the lowest expense ratios.

The single most important investment decision inside a 401(k) is minimising expense ratios. A 1% higher expense ratio on $100,000 costs approximately $30,000 over 20 years in forgone compounding.

Early withdrawal and 401(k) loans

Withdrawals before age 59½ trigger ordinary income tax plus a 10% early withdrawal penalty. On a $20,000 withdrawal at a 22% bracket: $4,400 tax + $2,000 penalty = $6,400 lost, leaving $13,600. Exceptions to the 10% penalty include permanent disability, certain medical expenses, and separation from service at age 55+ (for that employer's plan).

A 401(k) loan allows you to borrow from your own balance (up to 50% of vested balance or $50,000, whichever is less) and repay with interest — to yourself. No tax or penalty if repaid within 5 years. Risk: if you leave your employer while the loan is outstanding, you must repay the full balance within 60–90 days or it is treated as a distribution (triggering tax + penalty).

What happens to your 401(k) when you change jobs?

• Roll over to new employer's 401(k): Simplest for consolidation. Direct rollover (institution to institution) avoids tax withholding.
• Roll over to a traditional IRA: More investment options; no longer in employer control. Most flexible long-term choice.
• Leave it with former employer: Allowed if balance exceeds $5,000. Creates account fragmentation over a career.
• Cash out: Do not do this unless absolutely necessary. Tax + 10% penalty can consume 30–40% of the balance.

Key takeaways

• A 401(k) reduces your taxable income today; all growth is tax-deferred until withdrawal in retirement.
• Always contribute at least enough to capture the full employer match — it is a guaranteed 50–100% return before any market performance.
• 2026 limits: $23,500 employee contribution ($31,000 age 50+; $34,750 age 60–63).
• Traditional 401(k) saves tax now; Roth 401(k) generates tax-free retirement income — both can be used in the same plan.
• Choose low-cost index funds or target-date funds inside the plan — minimising expense ratios is the highest-ROI 401(k) decision after capturing the match.

Frequently asked questions

What is a 401(k)?

A 401(k) is an employer-sponsored retirement savings account funded with pre-tax payroll contributions. Contributions reduce your taxable income for the year; money grows tax-deferred; withdrawals in retirement are taxed as ordinary income. In 2026, the employee contribution limit is $23,500 ($31,000 if 50+).

What is a 401(k) employer match?

An employer match is additional money your company contributes to your 401(k) based on your own contributions. A common example: "100% match on the first 4% of salary" means contributing 4% of your $80,000 salary ($3,200) earns you an additional $3,200 from your employer — a 100% guaranteed return. Always contribute at least enough to capture the full match.

What is the difference between a traditional and Roth 401(k)?

Traditional 401(k): pre-tax contributions reduce taxable income now; withdrawals are taxed in retirement. Roth 401(k): after-tax contributions with no upfront tax break; qualified withdrawals in retirement are completely tax-free, including all growth. Both share the same $23,500/$31,000 annual limit.

What happens to my 401(k) when I leave my job?

Roll over to your new employer's 401(k) or to a traditional IRA — both preserve tax-deferred status with no tax or penalty. Do a direct rollover (institution to institution) to avoid mandatory 20% withholding. Cashing out triggers income tax plus a 10% penalty — avoid unless it is an emergency.

Can I take money out of my 401(k) early?

Yes, but early withdrawals before age 59½ trigger income tax plus a 10% penalty. A $20,000 withdrawal at a 22% bracket costs $6,400 in taxes and penalties. Exceptions to the penalty include permanent disability, certain medical expenses, and age 55+ separation from service (for that employer's plan). A 401(k) loan is often the better alternative for short-term cash needs.